The present invention relates to a device for indicating exposure to an impact, adverse temperature and/or humidity particularly, but not exclusively, useful for portable electronic equipment such as laptop computers, digital cameras and audio/visual devices.
Portable electronic equipment such as laptop computers, digital cameras and audio/visual equipment include sensitive electronic components. These equipment are usually covered by a manufacturer""s warranty where the manufacturer will repair or replace the product in the event of a defect (eg. faulty workmanship or faulty components), for a limited period after purchase. While such equipment are usually designed to withstand minor bumps and minor variations in temperature and humidity, they are not designed for and should not be exposed to impacts (eg. dropping a device onto the ground or table) and adverse temperature and humidity (eg. exposing the device to direct sunlight, snow, rain, hot/cold/humid environments), which may damage the product. Manufacturers"" warranties do not cover damage to these devices when exposed to any of such adverse conditions.
Often, devices damaged by exposure to adverse conditions are sent back to the manufacturer for repair under warranty. The customers may claim that their equipment was not exposed to any adverse condition. Apart from possible physical defects on the device resulting from an impact, there is presently no method for determining whether the product was exposed to any adverse condition. Currently, the manufacturers of many portable and mobile devices are not employing any means of determining exposure to such adverse conditions.
It would thus be desirable to provide a device which can reliably indicate to a repairer whether the faulty device has been exposed to any of such adverse conditions, in order to dispute a claim for warranty repair and avoid the associated costs.
There have been numerous attempts at providing devices for indicating exposure to an impact, adverse temperature or humidity, or combinations thereof, for various specific applications.
An impact sensor is disclosed in JP 2001-099854 (Akebono Brake Ind Co Ltd). This publication provides a device which can detect and display an impact such as a fall. In this device, a spherical shell which contains a coloured liquid is movably contained within an outer case which is attached to a portable electronic device. When the outer case is exposed to an impact, the shell is designed to break to spill the coloured liquid inside the outer case, giving a visual indication that the electronic device has been dropped.
Another impact sensor is disclosed in JP 11-326364 (Matsushita Electric Works Ltd). This publication provides a device having a body, the inside of which is partitioned into upper and lower housing spaces separated by a partition plate. Inside the upper housing space, a metal sphere is displaceably supported by three springs in all planar directions parallel to the partition plate. Inside the lower housing space, a printed-circuit board on which circuit components are mounted is located. A detecting coil mounted on the printed-circuit board is arranged under the metal sphere when the metal sphere is in a rest position (no shock force state). High-frequency magnetic fluxes are then generated from the detecting coil. Since an eddy-current loss generated on the surface of the metal sphere changes according to the displacement of the metal sphere, an impact can be detected.
Another impact sensor is disclosed in U.S. Pat. No. 5,551,279 (Quick). This US patent provides an impact gauge for determining the cumulative impact energy along a single axis. The device includes a housing having an elongated chamber with a pair of bendable members cantilevered into the chamber. An impacting member is positioned in the chamber with the impact member having sufficient mass so that when the housing is subjected to an impact, the inertia of the impacting member is sufficient to permanently bend the bendable member. One can then measure the degree of bend of the bendable member which can be correlated with impacts of measured strength to determine the accumulated impact energy absorbed by the impact gauge.
Another impact sensor is disclosed in U.S. Pat. No. 4,470,302 (Carte). This US patent provides an indicating shipping accelerometer having a transparent tube within which an inertial mass moves relative to a scale affixed to the transparent tube. The movement of the mass gives an indication of the maximum shock incurred in either direction of the tube""s longitudinal axis. Springs on either side of the inertial mass maintain the inertial mass in its initial position.
Another impact sensor is disclosed in U.S. Pat. Pat. 4,361,106 (Eklof). This US patent provides a device for providing a non-resettable visual indication of a shock above a predetermined value which is sustained by an object carrying the device. The device includes a transparent dome-like housing having a chamber, and an indicating body within the chamber. Prior to being subjected to a force above the predetermined value, the indicating body is maintained in a first position and when subjected to a force above the predetermined value is irreversibly released to a second position.
A temperature sensor is disclosed in U.S. Pat. No. 5,622,137 (assigned to Trans World Services). This US patent provides a disposable temperature sensor comprising a rigid substrate having a coloured patch covered by a thermochromic material which obscures the colored patch. The thermochromic material, which has a color which completely obscures the underlying colored patch, is selected to have a melting or solidus point such that when the thermochromic material is exposed to a predetermined temperature, the thermochromic material permanently changes to a relatively transparent color whereby the colored patch on the substrate is rendered visible through the thermochromic material. When fitted to a device, the sensor gives a visual indication that the device has been exposed to a predetermined temperature.
Another temperature sensor is disclosed in U.S. Pat. No. 5,325,721 (assigned to Minnesota Mining and Manufacturing Company). This US patent discloses a device for selectively indicating strain, which can also be used to determine exposure of an article to a given low temperature. The device comprises a layer of polymeric binder that is stiff below a preselected stiffening temperature. Distributed in or adjacent to the binder layer are microcapsules containing an indicating means. When the binder is stiff, minor flexure of the device causes rupture of the microcapsules and releases the indicating means. The device has a non-stiff state above the stiffening temperature such that a given strain applied to the binder layer in the non-stiff state will not release the indicating means. The device also has a stiff state below the stiffening temperature such that the same given strain applied to the binder layer in the stiff state will release the indicating means. The microcapsules can be made of a thermoplastic material such that the integrity of the shell capsules is thermally compromised at a predetermined temperature above the stiffening temperature, whereby heating of the device also releases the indicating means. Also, the device can further comprise a self-activating means for applying strain to the binder layer, such that when the temperature of the device is below the stiffening temperature, the self-activating means imparts sufficient strain so that the microcapsules are ruptured. The means for applying strain can comprise two materials having different coefficients of thermal expansion, such that the device flexes when the device experiences a change in temperature over a predetermined range. Alternatively, the means for applying strain is a bimetallic strip in intimate contact with the binder layer.
Another temperature sensor is disclosed in U.S. Pat. No. 4,931,420 (assigned to Mitsui Toatsu Chemicals, Inc.). This US patent discloses a temperature history indicator for goods which must be stored at a certain temperature or lower. When the storage temperature of such goods rises higher than the certain temperature over a non-permissible time period, this fact can be visibly shown by development or change of color caused by chemical matters in the indicator.
Another temperature sensor is disclosed in U.S. Pat. No. 3,877,411 (assigned to Railtech Ltd). This patent discloses a temperature indicator bolt having a shallow depression formed in the bolt head. A wafer type indicator element is retained in the shallow depression. The indicator element is impregnated with a chemical substance having indicating properties responsive to the predetermined temperature, such that the color of the substance will change and remain changed when the bolt is subjected to the predetermined temperature.
Another temperature sensor is disclosed in U.S. Pat. No. 2001/0046451 (Patel). This reference discloses a device for detecting temperature exposure of an article below a threshold temperature including an indicator which changes color when the article is exposed to a temperature below the threshold temperature.
A humidity sensor is disclosed in U.S. Pat. No. 5,875,892 (assigned to Humidial Corporation). This US patent discloses a packaging container having a humidity indicator system. The humidity indicator system includes a humidity indicator element, a humidity comparison element and a securing system for securing the humidity indicator element to the packaging container. The humidity indicator element is formed from a hydrophilic blotter substrate onto which is placed a humidity indicator solution which is sensitive to humidity and which readily discloses the level of humidity in the air surrounding the indicator element by changing its color depending on the level of humidity.
Another humidity sensor is disclosed in U.S. Pat. No. 2002/0000184 (Paton and Mani). This US Patent provides an elapsed time indicator for controlled environments. Exposure time is determined by a device which is sensitive to an environmental substance in a controlled environment. Embodiments include a humidity sensitive timer treated with a cobalt salt which changes colors after a certain exposure time within the controlled environment. Elapsed time is measured by exposing the timer to a humidity controlled environment and monitoring the timer for a change in color.
Another humidity sensor is disclosed in U.S. Pat. No. 4,098,120 (assigned to Minnesota Mining and Manufacturing Company). This US patent provides a humidity indicating device suitable for visibly indicating exposure to a selected humidity level or for indicating a humidity-time history. The device comprises in combination a deliquescent compound, a liquid absorbent wick, and an indicating means. The change in properties of deliquescent compounds are employed to indicate a particular humidity level or a humidity-time history.
Another humidity sensor is disclosed in U.S. Pat. No. 3,952,746 (Summers). This US patent provides a humidity indicator for a diaper including a moisture impervious outer sheet and a moisture absorbent inner sheet. A transparent opening is formed in the outer sheet either for viewing a moisture indicator strip behind the outer sheet or for exposing the moisture indicator strip on the outside of the outer sheet to communication with the moisture in the absorbent inner sheet.
It is the object of the present invention to provide an inexpensive, unresettable, miniature sensing and indicator device for attachment to mobile and portable devices which will allow a repairer to determine whether a device has been exposed to at least one of mechanical impact, temperature or humidity beyond its design, which will help manufacturers detect fraudulent warranty claims.
In one form, there is provided an impact sensor for indicating exposure of an electronic equipment to a predetermined impact force. The impact sensor has a hollow case, a mass within the case, and a number of wire filaments supporting the mass within the case. Exposure of the sensor to the predetermined impact force results in a force acting on the mass sufficient to cause at least one of the filaments to break. The breaking of at least one of the filaments indicates to a repairer that the electronic equipment has been exposed to the predetermined impact force.
In another form, there is provided a temperature sensor for indicating exposure of an electronic equipment to a predetermined upper and/or lower threshold temperature. The temperature sensor has a base and a snap action bimetallic strip which bends and snaps into place when exposed to a change in temperature. The first end of the strip is fixed to the base such that the second end thereof can move along the base with the change in temperature. Two wire filaments are attached to opposite sides of the second end of the strip. The other end of each filament is attached to the base. When the sensor is exposed to the predetermined upper or lower threshold temperature, the strip bends sufficiently to cause at least one the filaments to break. The breaking of at least one the filaments provides an indication of the exposure of the electronic equipment to the predetermined upper or lower threshold temperature.
In addition to the snap action bimetallic strip, the temperature sensor includes visual indicators which show the occurrence of exposure to an upper or lower threshold temperature. Exposure to the upper threshold is indicated by a change in color of a thermochromic chemical. Exposure to the lower threshold is indicated by a colored liquid in a capillary tube.
In another form, there is provided a humidity sensor for indicating exposure of an electronic equipment to a predetermined humidity level. The humidity sensor has a base and a plate mounted on the base which expands when exposed to moisture. A wire filament is attached between the base and a top portion of the plate. Exposure of the sensor to the predetermined humidity level results in expansion of the plate sufficient to cause the filament to break. The breaking of the filament thus indicates exposure of the electronic equipment to the predetermined humidity level.